This invention relates to pothole repair on roadways and highways.
Potholes are a common occurrence on roadways and develop over time as a result of a weakness in the original roadway installation. This weakness can be the result of an improper compaction of the roadway where, over time and cyclic loading from vehicular traffic, small cracks are created, particularly at joints, after which water can seep into the cracks and propagate the crack further; either by the hydraulic force created by the cyclic loading, or from the water freezing in cold environments.
Potholes are formed by rainwater flowing through cracks in old or weakened asphalt. The water is soaked up by the mixture of rock, gravel, and sand that supports the road. Vehicles passing over the road force water through the soggy roadbed, eventually causing erosion. Asphalt sinks into the eroded portions of the roadbed and eventually causing cracks under the continued impact of vehicle tires. This causes chunks of asphalt to come loose.
After a pothole is formed, the repair typically comprises the placement of a sufficient amount of asphalt to fill the pothole. This asphalt is, at the time of placement, soft and compressible. Following placement, the asphalt is compressed so that it is substantially level with the overall road surface.
Problems can occur frequently with this sort of repair activity. First, the asphalt may not have been sufficiently compressed and allowed to cure properly. Before becoming fully cured, asphalt is very pliable and prone to developing stress cracks, particularly at or near the joint edge located adjacent to the surrounding road surface. This portion of the asphalt fill is susceptible to crack development due to its proximity on one side to a rigid, cured road surface and on the other side to pliable, uncured asphalt. In addition none of the aggregate filler crosses the boundary, leaving an unreinforced zone at the joint. Slight cracks developed soon after application can propagate as a result of water intrusion, and freezing. The interface between asphalt fill perimeter and existing road surface can develop pathways for rainwater to collect below the pothole repair surface causing erosion.
Over time, the asphalt fill will cure. However, because of real world situations, the fill does not have the necessary time to cure completely before being subjected to weathering and repetitive load conditions resulting from vehicular traffic. This often times results in the same locations being repaired over and over. Thus, a problem with present methods for repairing potholes is that the repair oftentimes is only a temporary fix, and, over time, the repetitive repair results in increasingly high repetitive costs.
Expenditures caused by potholes are not limited to the cost of road repair. It has also been reported that the damage to cars have cost insurance companies approximately five billion dollars in 2010 alone.